Discrete Mathematics and Its Applications, Seventh Edition

by
Rosen, Kenneth

Chapter 6 - Section 6.1 - The Basics of Counting - Exercises: 8

Answer

People can have 15600 different 3 letter initials without repeating the same letter.

Work Step by Step

We assume only capital alphabets (A - Z)
The first letter has 26 choices
The second letter has 25 choices (we cannot choose the first letter again).
The third letter has 24 choices (we cannot choose first or second letter again).
So, total ways = 26 x 25 x 24 = 15600